This invention relates to an apparatus for rerounding deflected sewer, water or other pipes in situ and particularly relates to an improved apparatus for rerounding such pipes.
When flexible pipes or conduits such as, for instance, plastic water or sewer pipes are buried, the pipes may be deflected over time by the weight of the backfill material. The amount of deflection depends, among other factors, on the type of soil, the density of the soil, the placement of the pipe in the soil and the moisture content of the soil. Government regulations have been promulgated which define the maximum allowable deformation of the internal diameter of such pipes. Historically, when such deflection was detected, the pipes had to be dug up and the bedding material along the sides of the pipes and under the haunches of the pipes had to be recompacted and the entire trench had to be backfilled. This procedure was expensive, time consuming, and disruptive. Furthermore, this procedure did not insure that the deflection problem would not occur again.
Prior art devices have been provided to reround such deflected pipes in situ. In my prior patent, U.S. Pat. No. 4,309,128, the specification of which is incorporated herein by reference, an apparatus is disclosed comprising a cylindrical shell having a diameter which is slightly less than the diameter of the pipe to be rerounded. An air motor is mounted inside the shell for driving a vibrator. The entire apparatus is pulled through a pipe and the air motor is operated to cause vibrations to be set up in the apparatus for compacting the backfill. Deflected pipes may therefore be rerounded in situ, thus eliminating the necessity to dig up such deflected pipes and saving considerable expense and time.
One problem with the prior art devices is that insufficient horsepower is developed by the air motor. It is, of course, preferable that a substantial amount of horsepower is developed with a relatively compact air motor whereby substantial compaction of the backfill may take place. In the prior art device disclosed in U.S. Pat. No. 4,309,128, a commercial air motor was used to drive the crankshaft of the apparatus. While the rerounding device worked satisfactorily for many applications, this commercial air motor did not deliver as much horsepower as desired.
Another problem with the prior art rerounding devices has been that standard commercial air motors were designed only for intermittent operation and not for a continuous operation. It is desirable in the operation of rerounding devices to continuously operate the air motor as the rerounder is pulled through a considerable length of conduit. However, if the prior art air motors were operated continuously, the life of such air motors was substantially limited because of wear. Such wear is due to the high speeds at which air motors operate, the materials used in prior art air motors and furthermore, corrosion due to the environment in which the rerounding devices are operated. Corrosion is especially a problem in the use of the rerounding devices in coastal areas where the salt and humidity content of the air are particularly high.
A further problem with prior art rerounding devices was that adequate lubrication of the crankshaft bearings of the rerounder was difficult to accomplish. In particular, since the air which was expelled from the air motor was exhausted from the end of the rerounding device which is opposite to the end of the rerounding device at which the air motor was located, pressures would be set up in the rerounding device which would blow the lubrication out of the bearings and therefore leave the bearings inadequately lubricated. Since the crankshaft of the rerounding device rotates at approximately 4,000-5,000 RPM, and due to the presence of substantial levels of moisture in compressed air, lubrication of the bearings is crucial during continuous operation of rerounding devices. In the prior art rerounding devices disclosed in U.S. Pat. No. 4,309,128, the cavity of the rerounding device was about 1/3 filled with oil for lubricating the bearings whereby air pressure differences did not affect lubrication. However, it is desired to eliminate the need to fill the cavity of the rerounding device with oil.
A yet further problem with the prior art rerounding devices was that heat generated in the crankshaft bearings was not adequately dissipated, thus causing the bearings to heat up substantially and reducing the life thereof. The bearing heating problem was made worse by the fact that compressed air used by the air motor is at a considerably higher temperature than the ambient air, thus adding further to the bearing heating problem.
It is therefore desired to provide an improved rerounding apparatus having a compact and efficient air motor which is adapted to operate continuously. It is furthermore desired to provide an improved rerounding apparatus having an improved crankshaft bearing structure wherein the bearings are cooled by the air exhausted from the air motor and wherein the heat generated in the bearings is further dissipated from the bearings through the bearing support structure.
A yet further object of the present invention is to provide an improved rerounding apparatus including structure to equalize pressures across the crankshaft bearings in order to prevent lubricant from being blown out of the bearings.